Paper may be formed from short, flexible fibers that are processed, for example, to form sheets. During processing, many chemicals and materials may be added to improve the properties of paper for a particular use. For example, whitening agents may be added during processing to increase the whiteness and/or brightness of the resulting paper.
Certain common whitening agents function by making use a phenomenon known as fluorescence. For example, “fluorescent whitening agents” (FWA's) can absorb light having relatively short wavelengths (e.g., ultra-violet or near ultra-violet light) and emit light having a longer wavelength (e.g., visible light). This effect leads to an increase in the apparent whiteness and/or brightness of the resulting paper. Examples of common fluorescent whitening agents include diaminostilbene compounds.
However, fluorescent whitening agents are characterized as being poisonous and/or deleterious substances by the Food and Drug Administration, in part, because they can potentially cause health problems in humans if absorbed into the body. If food is packaged with paper that includes fluorescent whitening agents, it is possible for the agents to pass from the paper to the food. As a result, federal regulations limit the content of fluorescent agents in paper products intended for contact with food (i.e., food grade paper).
The safety concerns and regulations have, in particular, limited the ability to use recycled paper in food grade applications. Recycled paper typically is processed using waste paper produced from multiple sources, many of which oftentimes include fluorescent whitening agents. Thus, it is difficult (or impossible) to prevent the presence of such whitening agents during the processing of recycled waste paper. If not eliminated, such whitening agents are incorporated into the final paper product which, as noted above, renders the product unsuitable for food grade applications.